Dishwasher With a Sorption Drier and Method For the Operation Thereof

ABSTRACT

A method is provided for operating a dishwasher with at least one partial program step that includes heating a rinsing solution to a nominal temperature. Air that is heated by a heating device and used for desorption of a reversibly dehydratable material is conducted from a washing container of the dishwasher or ambient air is conducted through a sorption column with reversibly dehydratable material into the washing container in order to heat the rinsing solution and/or items to be washed. The heating device continues to operate after the desorbed state of the reversibly dehydratable material has been attained until the nominal temperature of the rinsing solution is reached.

The invention relates to a dishwasher with a sorption drier. Theinvention also relates to a method for operating a dishwasher with atleast one partial programme step with rinsing liquor that is to beheated to a nominal temperature, e.g. “Clean”, wherein air that isheated in this partial programme step by a heating device and is usedfor desorption of a reversibly dehydratable material and/or ambient airis conducted from a rinsing container of the dishwasher by a sorptioncolumn with reversibly dehydratable material into the rinsing containerin order to heat the rinsing liquor and/or items to be washed.

As is well known, conventional dishwashers have a washing process whoseprogramme sequence generally consists of at least one “Prewash” partialprogramme step, a “Clean” partial programme step, at least one“Intermediate Wash” partial programme step, a “Clear Wash” partialprogramme step and a “Drying” partial programme step. In order toincrease the cleaning effect the rinsing liquor is in this case heatedbefore or during a partial programme step. The rinsing liquor isnormally heated by means of electric heating devices. Different dryingsystems are known for drying the items to be washed in a dishwasher.

A dishwasher of the type just mentioned is disclosed in DE 20 16 831, inwhich the air is conducted from the rinsing container via a sealableopening in the wall of the rinsing container on reversibly dehydratablematerial and from there via an opening to the outside. The desorption ofthe reversibly dehydratable material takes place during thenon-operating phase of the dishwasher, the water vapour formed therebybeing conducted to the outside via the opening. The dishwasher describedis disadvantageous from the energy viewpoint because the regeneration ofthe reversibly dehydratable material takes place during a non-operatingphase of the dishwasher, i.e. at a time when none of the partialprogramme steps already described is being carried out. A furtherdisadvantage consists in the fact that the possibility of damage to thesurrounding kitchen furniture cannot be ruled out because of thedischarge of the water vapour formed during the regeneration of thereversibly dehydratable material to the outside. In this case theregeneration is associated with an additional energy requirement whichis added to the energy required during the partial programme steps.

In order to minimise the energy expenditure when operating a dishwasher,DE 103 53 774.0 of the applicant discloses a dishwasher with a rinsingcontainer and devices for washing dishes by means of rinsing liquor,which dishwasher has a sorption column connected in an air-conductingmanner to the rinsing container and containing reversibly dehydratablematerial, wherein on the one hand the sorption column is used to dry thedishes and on the other hand the thermal energy used for desorption ofthe sorption column is at least partially used for heating the rinsingliquor and/or the dishes.

To solve this same problem DE 103 53 775.9 of the applicant proposes,for operating a dishwasher, to conduct air in the at least one “Drying”partial programme step from a rinsing container and/or from ambient airthrough a sorption column and into the rinsing container, the sorptioncolumn containing reversibly dehydratable material and moisture beingextracted from the air during its passage.

Heating of the items to be processed is normally no longer necessary inthe partial programme step preceding the “Drying” partial programme stepdue to the use of reversibly dehydratable material with a hygroscopicproperty, e.g. zeolith. This allows a considerable energy saving.

EP 0 358 279 B1 discloses a device for drying dishes in a domesticdishwasher in which the rinsing liquor is heated by a heater arrangedoutside the rinsing container, preferably an electric geyser, a largelyclosed drying system being provided here in which air circulates fromthe rinsing container via a drying device that can be regenerated byheating and from this device back into the rinsing container. Here thedrying device consists of a drying container in thermal contact with theheater, which container is filled with a drying means adsorbing themoisture. Because the drying container is connected to the heaterprovided in any case for heating the rinsing liquor, the drying deviceis immediately operational after completion of the rinsing process. Thedrying means is in this case placed at least partially around theheating elements as a jacket so that the drying means can be heated andhence dried in the drying container during each heating process.

The drying container is designed as a double-wall hollow cylinder intowhich the drying material is introduced. The inlet and outlet openingfor connection to the closed air system are arranged diagonally oppositeone another. The disadvantage of this is that it gives rise to arelatively flow resistance, with the result that the fan provided forconveying the air flow must be operated at very high power. This has anegative effect in terms of noise development and energy consumption.

Because of the structural design of the sorption drier, which requiresinhomogeneous introduction of heat into the drying material, thedesorption is time consuming and may also lead to local overheating ofthe drying means and hence to its irreversible damage. The desorption isalso difficult because the heater is arrange din the centre of thedouble-wall hollow cylinder and radial distribution of heat to thedrying means close to the outer hollow cylinder wall is hardly possiblebecause of the air flowing axially past it.

The object of this invention is therefore to provide a method foroperating a dishwasher and a dishwasher, particularly a domesticdishwasher, with which it is possible to shorten the length of a rinsingprogramme with a plurality of partial programme steps.

This object is achieved by the method according to the invention withthe features according to Claim 1 and by a dishwasher with the featuresof Claim 6. Advantageous further developments of this invention arereproduced in the dependent claims.

In the method according to the invention for operating a dishwasher, inparticular a domestic dishwasher, with at least one partial program stepwith rinsing liquor that can be heated to a nominal temperature, e.g.“Clean”, where air heated in this partial programme step by a heatingdevice for desorption of a reversibly dehydratable material is conductedfrom a rinsing container of the dishwasher and/or ambient air isconducted through a sorption column with reversibly dehydratablematerial into the rinsing container for heating the rinsing liquorand/or the items to be washed, the heating device continues to operateafter a desorbed condition of the reversibly dehydratable material isattained until the nominal temperature of the rinsing liquor is reached.

The term desorbed condition of the reversibly dehydratable material isunderstood in this invention to mean that the reversibly dehydratablematerial is completely or almost completely dehumidified.

In other words this means that the rinsing liquor is not heated by aconventionally designed (water) heating device but that the energyexpended for the desorption is used during a partial programme step withrinsing liquor to be heated for heating the rinsing liquor. However,desorption is normally fully completed at a time when the rinsing liquorhas no yet been brought to the required nominal temperature. Theinvention therefore proposes continuing to operate the (air) heatingdevice used for the desorption so that air is heated in the sorptiondrier and fed to the rinsing container. Because of the introduction ofhot air into the rinsing container the rinsing liquor and/or the itemsto be washed continue to be heated until the nominal temperature of therinsing liquor is reached. Since very high temperatures are reachedduring the desorption process in the sorption drier, more precisely inthe sorption column, the rinsing liquor is heated very quickly.

According to a suitable design the desorbed moisture is fed to therinsing container. During the desorption process, which takes placeduring a partial programme step with rinsing liquor to be heated, thereversibly dehydratable material for desorption is heated to very hightemperatures. Here the stored liquid escapes as hot water vapour.Because the fan is operating the water vapour is introduced into arinsing container of the dishwasher and the air in the rinsing containeris therefore also heated. The introduction of the hot water vapour andthe heated air into the rinsing container (rinsing container) issufficient to heat the rinsing liquor and/or the dishes to such atemperature that the difference until the nominal temperature is reachedcan be attained by continuing to operate the sorption drier.

In a further suitable design provision may also be made for anadditional heating device to be operated for heating the rinsing liquorbefore and/or after the desorbed condition of the reversiblydehydratable material is attained. This shortens the heating time andtherefore reduces the duration of the partial programme step for therinsing liquor to be heated.

The additional heating device is suitably arranged in the rinsing liquorcircuit and heats the rinsing liquor directly. In other words this meansthat the additional heating device is designed as a water heatingdevice, but compared to a classic heating device, such as that describedin EP 0 358 279 B1, for example, it can be dimensioned much smaller. Theadditional heating device may alternatively also be designed as an airheating device in the circuit of the sorption drier.

In a further advantageous design the air is passed through a fan thatcan be operated at a variable speed, the speed of the fan beingestablished according to a desired duration of the partial programmestep. According to an advantageous design a dishwasher can be operatedduring the partial programme step with rinsing liquor to be heated at aconstant, low and hence noise-optimised speed. On the other hand it ispossible to increase the speed of a controlled fan so that the heatingprocess for the rinsing liquor is accelerated. Such a time-reducedrinsing programme is in this case accompanied by increased operatingnoise. It is therefore advantageous for the speed of the fan to beselected in a plurality of stages by a control element of thedishwasher. In other words a function can be provided in the controlelement of the dishwasher which enables the user to select a “Fast RinseProgramme” actively, which means that the user then actively opts forincreased noise development.

A dishwasher according to the invention has the same advantages as thosedisclosed in connection with the above method.

In a dishwasher designed according to the invention, particularly adomestic dishwasher, with a rinsing container and devices for rinsingitems to be washed by means of rinsing liquor, and with a sorption drierhaving a sorption column connected in an air-conducting manner to therinsing container and containing dehydratable material, where on the onehand the sorption column is used to dry the dishes and on the other handthe thermal energy used for desorption of the sorption column is usedfor heating the rinsing liquor in the rinsing container and/or the itemsto be washed, the rinsing liquor can be heated to the nominaltemperature required in the partial programme step concerned by means ofthe sorption drier.

One advantage of this lies in the fact that this allows a very simplestructure for such a dishwasher since it is possible to dispense with aclassic (water) heating device. In principle the dishwasher may bedesigned as described in DE 103 53 774 and/or DE 103 53 775 of theapplicant, whose contents are incorporated in this application whereappropriate. The machine described here is distinguished by its controlsystem and the operation of the sorption drier and/or by the design ofthe components of the sorption drier, since the latter continues to beoperated by pure dehydration of the sorption column until the nominaltemperature of the rinsing liquid is reached. In the case of adishwasher according to the invention the main control for achieving thedesired operation and/or the power of the heating device and fan, aswell as the volume of the sorption column are modified, e.g. in terms oftheir geometric design, and are matched to each other so that a furtherincrease in the temperature of the rinsing liquor is possible merely byoperating the heating device and the fan.

According to a preferred feature air is conducted from the rinsingcontainer and/or from the ambient air during a partial programme stepwith rinsing liquor to be heated, preferably during the “Clean” and/or“Prewash” and/or “Clear Rinse” partial programme step through thesorption column and into the rinsing container.

According to a further preferred feature the rinsing container has anoutlet with a pipe to the sorption column, wherein the pipe ispreferably provided with a shutoff valve and, in the direction of flow,then preferably an inlet valve for the ambient air, and the rinsingcontainer has an inlet with a pipe from the sorption column, a fan beingarranged in the pipe to the sorption column which introduces at leastsome of the air in the rinsing container or from the ambient air of thesorption column, at least temporarily. In a preferably closed air systemthe possibility of exchange of contaminated air from the atmosphere iscompletely excluded, thereby preventing recontamination of the items tobe washed. The fan can easily be activated so that the use of thesorption column can be precisely controlled.

An electric heating device is suitably arranged for desorption of thereversibly dehydratable material and for heating the rinsing liquorand/or the items to be washed. This device is preferably arranged in thereversibly dehydratable material or in the pipe to the sorption column.

It is also appropriate for the fan of the sorption drier is designed sothat it can be speed-controlled by a main control unit of the dishwasherin order to be able to control the rate of heating of the temperature ofthe rinsing liquor and/or the items to be washed. The speed of the fanmay in this case be selected preferably steplessly or in a plurality ofstages by a control element of the dishwasher.

The invention is explained in greater detail in the following by way ofthe exemplary embodiment of a method in a dishwasher represented in thedrawing.

The method according to the invention for operating a dishwasher with atleast one partial programme step with rinsing liquor to be heated to anominal temperature and/or with at least one “Drying” partial programmestep is implemented in the exemplary example described in a dishwasherwhich is constructed schematically, as described in DE 103 53 774 and/orDE 103 53 775 of the applicant. As is well known a dishwasher has arinsing process whose programme sequence generally consists of at leastone “Prewash” partial programme step V, a “Clean” partial programme stepR, at least one “Intermediate Wash” partial program step Z, a “ClearRinse” partial programme step K and a “Drying” partial programme step T.The drying is preferably carried out in the exemplary embodiment asdescribed in DE 103 53 774 and/or DE 103 53 775, the contents of whichare incorporated in this application, if appropriate. Here the FIGUREshows a typical temperature curve of the rinsing liquor during thesepartial programme steps. The FIGURE also shows both the operation in aconventional dishwasher and operation according to the method accordingto the invention.

The “Prewash” partial programme step V and the “Intermediate Wash”partial programme step Z are of subordinate importance for the methodsaccording to the invention, with the result that they are not consideredin detail in the following description. At the beginning of the “Clean”partial programme step R the rinsing liquor is normally heated to anominal temperature T_(nenn) in order to achieve the desired cleaningeffect. In an energy-optimised dishwasher with a sorption drier, asalready known from the state of the art, the desorption, i.e. theheating of the reversibly dehydratable material, also takes place duringthe “Clean” partial programme step R. The contents of DE 103 53 774and/or DE 103 53 775 are incorporated in this application, ifappropriate.

In order to heat the rinsing liquor it is now heated, according to theinvention, not directly by a water heating device but use is made of theenergy required for the desorption. For this purpose an (air) heatingdevice arranged in the sorption drier, which contains the reversiblydehydratable material, e.g. zeolith, is heated to a high temperature.During the desorption of the reversibly dehydratable material, air isconducted from a rinsing container, e.g. with an outlet, through thesorption column and then back into the rinsing container via an inlet,the air being heated by the heating device during its passage. In thiscase the air is sucked out of the rinsing container by means of a fanand forced through the sorption column. The hot water vapour escapingfrom the sorption column and the air, now heated, enter the rinsingcontainer through the inlet already mentioned and therefore meet thecirculated rinsing liquor and/or the dishes, which are heated thereby.

The sorption drier is normally operated only until the reversiblydehydratable material is fully desorbed, i.e. dehumidified (Section A inthe FIGURE). In the exemplary embodiment shown in the FIGURE, thiscondition is reached at a time t_(a) when the rinsing liquor and/or theitems to be washed have reached a temperature T_(Des). This temperatureis normally below the nominal temperature T_(nenn) to be achieved. Tobridge this temperature difference the heating device and the fan of thesorption drier now continue to be operated according to the invention,and hot air is conveyed to the rinsing container, until the circulatedrinsing liquor and/or the items to be washed reach the desired nominaltemperature (Section B). This condition is reached with suitabledimensioning of the sorption drier, in particular the power of theheating device, the speed of the fan and the arrangement and geometry ofthe sorption column at a time t_(b).

The method according to the invention enables a dishwasher to beprovided which may therefore dispense completely with a water heatingdevice. The rinsing liquor is heated advantageously in all partialprogramme steps by the air heating of the sorption drier that is of avery simple structure and can therefore be manufactured at low cost.

To enable the “Clean” partial programme step R to be carried out morequickly, i.e. in order to be able reach the desired nominal temperatureT_(nenn), an additional heating device may be provided according toanother variant of the invention, which device heats the rinsing liquorduring Section A and/or during section B to increase the temperaturefrom T_(Des) to T_(nenn), so that nominal temperature T_(nenn) isalready reached at time t_(c) (Section C). The additional heating devicemay optionally be designed as a water heating device, e.g. a geyser, oras an air heating device inserted in the air circuit. In both cases theadditional heating device can be dimensioned so that only a low heatingpower need be made available that is capable of bridging the missingtemperature difference between T_(Des) and T_(nenn). Not shown in theFIGURE, but quite obvious to a person skilled in the art, is the factthat regardless of the time when the nominal temperature T_(nenn) (inthe exemplary embodiment t_(b) or t_(c)) is reached, the heating phaseof the rinsing liquor is completed, resulting in a reduction in theprocessing temperature by the end of the “Clean” partial programme stepR. The extent to which the processing temperature falls and the durationof this fall depend on the type of cleaning programme carried out and onthe insulating characteristics of the dishwasher.

According to a further variant provision may also be made for the speedof the fan of the sorption drier to be increased during the “Clean”partial programme step R in order to achieve a further reduction in thetime until the nominal temperature T_(nenn) is reached. This could beprovided so that it can be pre-elected by the user of the dishwasher,e.g. by means of a control element.

In conventional dishwashers the items to be washed are dried byso-called intrinsic heat drying in the “Clear rinse” and “Drying”partial programme steps (Section 1). Here the rinsing liquor is heatedin the “Clear rinse” partial programme step, as a result of which theitems to be washed, clearly hot rinsed by the intrinsic heat of theitems to be washed thus developed, are automatically dried during thedrying process. To achieve this intrinsic heat drying the rinsing liquoris therefore heated in the “Clear rinse” partial programme step totemperature T_(K) and applied to the items to be washed by sprayingdevices. Because of the relatively high temperature of the rinsingliquor in the “Clear rinse” partial programme step, normally rangingfrom 65° C. to 75° C., a sufficiently quantity of heat is transferred tothe items to be washed so that the water adhering to the items to bewashed evaporates due to the heat stored in the items to be washed.

A considerable energy saving is achieved by the use of sorption driersbecause heating of the rinsing liquor in the “Clear rinse” partialprogramme step K is not necessary in principle in these devices (Section2), but can nevertheless be carried out to a small extent (Section 3).The drying is achieved in that air is conducted in the “Drying” partialprogramme step from the rinsing container and/or from ambient airthrough the sorption column into the rinsing container, the sorptioncolumn containing the reversibly dehydratable material extractingmoisture from the air during its passage. Because of the use ofreversibly dehydratable material with a hygroscopic property, e.g.zeolith, heating of the items to be processed is not normally necessaryin the partial programme step preceding the “Drying” partial programmestep (Section 2), but heating to low temperatures, e.g. up to 30° C.,can still be carried out during “Clear rinsing” (Section 3). Due toheating of the air by means of the sorption column, in which thecondensation heat of the water vapour is released, its moistureabsorptivity is increased during each passage through the sorptioncolumn, which results in an improvement in the drying result and to ashortening of the drying time. Additional heating of the air with asupplementary heating device in the “Drying” partial programme step,besides heating with the sorption column, and hence also heating of thedishes in dishwashers, for example, is not normally required because thethermal energy released in the sorption column is sufficient to heat theair to high temperatures, e.g. 70° C. The sorption column itself isheated by the condensation heat to temperatures of up to 160° C., forexample.

An acceleration of the drying process, which in conventional dishwasherstakes place by means of a time programme control system and lasts untiltime t₁, can be achieved by providing the fan whose speed can becontrolled steplessly or in a plurality of stages in the sorption drier.The adsorption process is accelerated by the increase in speed,resulting in a shortening of the drying time.

If increasing the temperature during the “Clear rinse” partial programmestep is dispensed with, drying can be terminated as early as time t₂(Section 2). A further reduction in drying time is achieved by theheating of the clear rinse temperature described above (Section 3),enabling drying to be completed at time t₃. Here it must be assumed thatthe drying efficiency and degree of drying of the items to be dried areidentical in all three variants.

Since the increase in the speed of the fan of the sorption drier isaccompanied by increased noise radiation, it is advantageous to havethis mode of operation carried out actively by a user of the dishwasher.This cold achieved, for example, by providing a suitable control elementwhich is connected to a main control system of the dishwasher and asuitable mode of operation.

This invention provides a method with which it is possible to operate adishwasher of the type mentioned economically and to minimise theassociated energy expenditure in a time-optimised manner.

1-13. (canceled)
 14. A method for treating crockery disposed in a washing container, comprising: subjecting crockery to at least a washing step, a rinsing step, and a drying step, with a rinsing solution being heated to a nominal temperature during at least one of the washing step, the rinsing step, and the drying step, and air being passed into contact with crockery during at least one of the washing, rinsing, and drying steps, such air that has been passed into contact with crockery being thereafter guided to a sorption drying device communicated with the washing container, the sorption container containing reversibly dehydratable material that operates to withdraw moisture from air during the passage of the air through the sorption drying device, and thermal energy acting to desorp the reversibly dehydratable material of the sorption drying device crockery to achieve a desorbed condition of the reversibly dehydratable material; heating with a heating device air during at least some of its passage through and between the sorption drying device and the washing container; and continuing to operate the heating device after a desorbed condition of the reversibly dehydratable material is attained until the nominal temperature of the rinsing solution is reached.
 15. The method according to claim 14 and further comprising supplying desorbed moisture to the washing container.
 16. The method according to claim 14 and further comprising operating an additional heating device for heating the rinsing solution during at least one of before and after the desorbed condition of the reversibly dehydratable material is attained.
 17. The method according to claim 16, wherein operating an additional heating device for heating the rinsing solution includes operating an additional heating device arranged in the rinsing solution circuit such that the rinsing solution is heated directly.
 18. The method according to claim 14 and further comprising conducting air during at least some of its passage through and between the sorption drying device and the washing container via a fan that can be operated at a variable speed, wherein the speed of the fan is established according to a desired duration of a partial programme step.
 19. A dishwashing machine comprising: a washing container; at least one device for washing crockery using a rinsing solution, the washing of crockery being performed in a plurality of partial programme steps and the rinsing solution being heatable to a nominal temperature; and a sorption drying device communicated with the washing container for the passage of air between the sorption drying device and the washing container, the sorption drying device containing reversibly dehydratable material that operates to withdraw moisture from air during the passage of the air through the sorption drying device, wherein, on the one hand, the sorption drying device is used to dry crockery being handled by the dishwasher and, on the other hand, thermal energy utilized for desorption of the sorption drying device is used to at least partially heat at least one of the rinsing solution in the washing compartment and crockery, and the sorption drying device being operable to heat the rinsing solution to the nominal temperature required in each partial programme step.
 20. The dishwasher according to claim 19, wherein air is conducted through the sorption column and into the washing container from at least one of the washing container and an ambient air source during a partial programme step with rinsing solution to be heated including, preferably, during a “Clean” partial programme step, a “Prewash” partial programme step or a “Clear rinse” partial programme step.
 21. The dishwasher according to claim 20, wherein the washing container has an outlet with a pipe to the sorption column, the pipe is preferably provided with a shutoff valve and with an inlet valve for the ambient air, in the direction of flow, and the washing container has an inlet with a pipe from the sorption column, wherein a fan is arranged in the pipe to the sorption column, which fan introduces at least some of the air in the washing container or from the ambient air of the sorption column, at least temporarily.
 22. The dishwasher according to claim 19, wherein an electric heating device is arranged for desorption of the reversibly dehydratable material and heating the rinsing solution and/or the items to be washed.
 23. The dishwasher according to claim 22, wherein the heating device is arranged in the reversibly dehydratable material or in the pipe to the sorption column.
 24. The dishwasher according to claim 21, wherein the fan of the sorption drier is formed by a main control unit of the dishwasher so that its speed can be controlled.
 25. The dishwasher according to claim 24, wherein the speed of the fan can be selected steplessly or in a plurality of stages by a control element of the dishwasher.
 26. The dishwasher according to claim 19, wherein the dishwasher is operable to perform a method for treating crockery disposed in the washing container that includes the steps of (a) subjecting crockery to at least a washing step, a rinsing step, and a drying step, with a rinsing solution being heated to a nominal temperature during at least one of the washing step, the rinsing step, and the drying step, and air being passed into contact with crockery during at least one of the washing, rinsing, and drying steps, such air that has been passed into contact with crockery being thereafter guided to the sorption drying device communicated with the washing container, the sorption container containing reversibly dehydratable material that operates to withdraw moisture from air during the passage of the air through the sorption drying device, and thermal energy acting to desorp the reversibly dehydratable material of the sorption drying device crockery to achieve a desorbed condition of the reversibly dehydratable material, (b) heating with a heating device air during at least some of its passage through and between the sorption drying device and the washing container, and (c) continuing to operate the heating device after a desorbed condition of the reversibly dehydratable material is attained until the nominal temperature of the rinsing solution is reached. 